An environmentally responsive self-driven flexible blade for stable motion and its preparation method

Abstract

The present invention provides a preparation method of an environmentally responsive self-propelled flexible blade with stable motion, which comprises the following steps: taking acrylamide and acrylic acid in a molar ratio of 5:1, taking potassium persulfate with a weight of 1% of the total weight of acrylamide and acrylic acid, adding a crosslinking agent, N,N,N',N'-tetramethylethylenediamine, sodium polyacrylate, polyethylene oxide, and polyvinyl alcohol, mixing them evenly in water, adding a mixture of Ti3C2TxMXene and TiO2 and copper sulfide nanoparticles, stirring evenly, performing electrostatic spinning, crosslinking with dopamine, and using Fe 3+ Ionic solution and Cu 2+ The flexible blade obtained by the present invention can achieve rapid, reversible, self-driven deformation with large deformation amounts within a narrow temperature range, and has an excellent number of "deformation-recovery" cycles, thereby providing the flexible blade with stable self-driven motion capabilities.

Description

Technical Field

[0001] The present invention belongs to the field of advanced materials and relates to self-driven flexible materials, in particular to an environmentally responsive self-driven flexible blade with stable motion and a preparation method thereof. Background Art

[0002] Since the 21st century, with the development of science and technology, smart medical care, wearable devices, industrial manufacturing, robots, etc. have put forward increasingly higher requirements for mechanical energy conversion devices, such as miniaturization, lightweight, flexibility, and intelligence. Traditional internal combustion engines and electric motors have encountered development bottlenecks due to their mechanism limitations.

[0003] To address these needs, research on self-actuated flexible materials has focused on achieving energy conservation and device flexibility. In existing self-actuated flexible material development, the driving source typically comes from changes in the natural environment. Generally speaking, when light, electric fields, and magnetic fields are used as driving sources, the material's strength, phase transitions, and operating frequency can be precisely and rapidly adjusted. However, flexible materials driven by chemical atmospheres, humidity, temperature, and pH typically require liquid or enclosed environments, impose strict environmental parameter requirements, and have longer response times.

[0004] Blades are commonly used components in mechanical equipment, often installed in aircraft or underwater devices. They need to swing or rotate to cause changes in air or water flow, allowing the related mechanical equipment to achieve motion. Currently, there is little research on blades with self-propulsion capabilities. This is because the driving force required by aircraft is large and the frequency is high, and existing materials cannot meet the requirements of aircraft blades. For blades in underwater equipment, the response time of existing self-propulsion materials is still long, making it difficult to achieve rapid deformation that can produce corresponding changes in water flow. In addition, the rigidity of the blade base material is generally large, further increasing the difficulty of preparing corresponding flexible blades.

[0005] Underwater devices typically operate in a low-power mode when their battery is low, maintaining basic mobility and slowly swimming toward their destination. While existing flexible materials cannot yet provide sufficient power for large underwater devices, research is underway to develop flexible blades that can slow the movement of smaller devices like robotic fish. This, in turn, could provide a self-propulsion method, enabling these devices to operate in an ultra-low-power mode with even lower power consumption.

[0006] To address this issue, the inventors envisioned using light emitted by a light-emitting device mounted on an artificial robotic fish as a driving source. This would allow the corresponding flexible material, acting as the flexible blades of a device like the artificial robotic fish, to self-deform under light exposure, thereby driving the device's motion. Currently, the theoretically feasible materials are photothermodeformable materials, which automatically deform in response to temperature changes under illumination. Therefore, the following focuses on thermally responsive materials.

[0007] Thermal energy, as one of the most commonly used forms of energy in production and life, has been widely studied and applied in the field of self-driven deformation materials. At present, the most studied materials in this field are low-melting-point alloys, shape memory polymers, hydrogels and carbon nanomaterials. There are many existing technologies that have studied low-melting-point alloys and shape memory polymers. For example, Ford [1] The liquid crystal elastomer / liquid alloy composite film used by et al. can change temperature through Joule heat and other methods, thereby producing stretching and deformation. At the same time, the composite film also has sensing properties. [2] et al. prepared a size-controllable light-driven shape memory polymer film, which produced a stable polymer network through cross-linking and could achieve reversible phase transition at room temperature through linear or polarized light.

[0008] Hydrogels are a type of material with a wide range of applications. They have the advantages of a wide source of raw materials, low preparation costs, and simple preparation methods. They are usually an important research object for corresponding advanced materials in order to industrialize them as soon as possible. Thermoresponsive hydrogels can be divided into two categories, one with a lower critical solution temperature (LCST) and the other with a higher critical solution temperature (UCST). For UCST hydrogels, when the temperature rises, the hydrogel absorbs water and expands, and when the temperature drops, the hydrogel dehydrates and shrinks; the opposite is true for LCST. Using this property, people have studied some thermo-induced deformable flexible materials, such as Zheng [3] et al. used LCST and UCST hydrogels to prepare a double-layer film structure. After the material was made into a bionic gripper, it was able to grasp objects in a variety of environments such as water, liquid paraffin, and air.

[0009] However, the response time of flexible materials prepared by existing thermoresponsive hydrogels is usually long. [3]The material prepared by et al. takes 10 minutes to complete the deformation required for grasping objects; while the response time of the film prepared by the current UCST (or LCST) is usually more than 20 seconds. If high-speed reversible deformation is to be achieved, the thickness of the prepared film must be controlled at the micron level. For example, Jiang et al. [4] used PNIPAM and polyurethane to prepare a hydrogel film self-propelled material. The PNIPAM layer thickness is about 100 μm, and when placed alternately in water at 4 ℃ and 40 ℃, it can produce reversible deformation with a response time of less than 1 second. Too thin a film is difficult to generate enough deformation force to drive the deformation of the blade base material, so it does not have the prospect of being used to prepare flexible motion that can drive underwater equipment. In addition, the temperature span for producing reversible deformation is large, which is also a defect of existing materials of this type.

[0010] At present, for optoelectronic flexible products, tens of thousands of charge and discharge cycles can usually be achieved, but for reversible deformable hydrogel products, it is still not easy to achieve multiple "deformation-recovery" cycles while maintaining the corresponding response time, especially when they are in a water environment for a long time. It should be pointed out that when the corresponding flexible product is fixed on a substrate material with greater rigidity, the number of "deformation-recovery" cycles that can be obtained will be even smaller. For example, Liao Jiexin [5] Prepared stimulus-responsive shape memory hydrogel - D4DMA 0.8 The number of cycles for the hydrogel was only 3 times.

[0011] In summary, developing the currently envisioned, theoretically feasible, and practical material for flexible blades in underwater equipment requires a flexible material that can be driven by a photothermal effect, is simple to prepare, and has a fast response time. This flexible material can then drive the deformation of a relatively rigid blade substrate. More importantly, flexible blades made from this material should be able to achieve a high number of deformation-recovery cycles, with minimal impact on deformation and response time, ensuring stable motion.

[0012] References cited in this section:

[0013] [1]Ford MJ, Ambulo CP, Kent TA, et al., A multifunctional shape-morphing elastomer with liquid metal inclusions, Proc. Natl. Acad.Sci., 2019, 116(43),21438-21444.

[0014] [2]Wang W., Shen D., Li X., et al., Light-driven shape-memory porous films with precisely controlled dimensions, Angew. Chem. Int. Ed., 2018, 57(8), 2139-2143.

[0015] [3]Zheng J., Xiao P., Le X., et al., Mimosa inspired bilayer hydrogelactuator functioning in multi-environments, J. Mater. Chem. C, 2018, 6(6),1320-1327.

[0016] [4]Jiang S., Liu F., Lerch A., et al., Unusual and superfasttemperature-triggered actuators, Adv. Mater., 2015, 27(33), 4865-4870.

[0017] [5] Liao Jiexin. Research on stimulus-responsive shape memory hydrogel and spontaneous actuation behavior[D]. South China University of Technology, 2019. Summary of the Invention

[0018] To address the shortcomings of existing technologies, one objective of the present invention is to provide a flexible material for blade skins that uses a photothermal effect as a driving force, is simple to prepare, and has a fast response time. This flexible material can be used to create flexible blades that can achieve rapid, reversible, self-driven deformation within a narrow temperature range. Furthermore, the resulting flexible blades must exhibit a high number of deformation-recovery cycles, while maintaining minimal deformation and response time.

[0019] In view of the above objectives, the present invention provides the following technical solutions:

[0020] A method for preparing an environmentally responsive self-propelled flexible blade capable of stable movement, the method comprising the following steps:

[0021] (1) Preparation of blade skin materials:

[0022] 1) Acrylamide and acrylic acid are prepared in a molar ratio of 5:1, potassium persulfate is added to a crosslinker, N,N,N',N'-tetramethylethylenediamine, sodium polyacrylate, polyethylene oxide, and polyvinyl alcohol in a solution containing 1% of the total weight of acrylamide and acrylic acid, and the mixture is uniformly mixed in water to obtain solution A;

[0023] 2) Add a mixture of Ti3C2Tx MXene and TiO2 to solution A at a weight ratio of 1:4-7, then add copper sulfide nanoparticles and stir evenly to obtain solution B;

[0024] 3) Electrospinning was performed using solution B as the electrospinning solution to obtain a fiber membrane, and the obtained fiber membrane was treated at 50-60°C for 1-3 hours; then the fiber membrane was placed in a dopamine aqueous solution and cross-linked with EDC and NHS; after cross-linking, it was immersed in Fe 3+ Ionic solution and Cu 2+ After 12 to 36 hours in the ion solution and washing the residual ions with water, the blade skin material is obtained;

[0025] (2) placing the skin material obtained in step (1) on the blade base material, and fixing it to obtain the environmentally responsive self-driven flexible blade with stable motion;

[0026] Among them, the volume ratio of N,N,N',N'-tetramethylethylenediamine to water is 1:250; the weight of sodium polyacrylate is 15% of acrylamide; the weight of polyethylene oxide is 15% of acrylamide, and the weight of polyvinyl alcohol is 20% of acrylamide; the weight ratio of Ti3C2Tx MXene to TiO2 is 1-2:1; the weight of copper sulfide nanoparticles is 10-20% of the weight of acrylamide; the concentration of dopamine aqueous solution is 10-50 mg / mL; Fe 3+ The concentration of the ion solution is 0.02mmol-0.1mmol; Cu 2+ The concentration of the ion solution is 0.02mmol-0.1mmol;

[0027] The blade base material includes a thin layer of PVC, and the thickness ratio of the base material to the skin material is not higher than 5:12.

[0028] During their research, the inventors of this invention developed a sensitive, self-propelled, photothermal flexible blade and have filed a separate patent application entitled "A Sensitive, Self-Propelled Photothermal Flexible Blade and Method for Its Preparation." The inventors will not elaborate on the experimental details of this invention.

[0029] The above patented technical solution can achieve a bending curvature of 0.19cm in 0.5s and 0.6s respectively in the range of 28~30℃ during the first cycle. -1However, when the inventors increased the number of cycles to 20, the bending curvature of 0.11 cm could only be completed in 1.7s and 2.3s in the range of 28-30℃. -1 Thermal deformation and recovery deformation; after 100 cycles, 0.1cm -1 The thermally induced deformation has reached 21s.

[0030] Therefore, in the present invention, how to increase the number of cycles is studied.

[0031] Hydrogel is a type of water-absorbing material. Although responsive hydrogels can expel some water to complete deformation according to environmental changes, after being immersed in a water environment for a long time, the hydrogel's suction force on water and the water extrusion force caused by deformation will gradually become unbalanced, and the suction force on water will dominate, thereby affecting the number of cycles of the responsive hydrogel.

[0032] At present, there are relatively few studies on preparing hydrogel materials containing multiple components by blending materials to solve the problem of low cycle number of responsive hydrogels. During the research, the inventor accidentally discovered that in the technical solution of the patent "A sensitive photothermal self-driven flexible blade and its preparation method", after replacing sodium polyacrylate with sodium polyacrylate, polyethylene oxide and polyvinyl alcohol, the cycle number of the flexible blade obtained was greatly improved. When the cycle number reached 310 times, it could still complete the bending curvature of 0.10cm in 1.2s and 1.6s in the range of 28~30℃. -1 thermally induced deformation and recovery deformation.

[0033] Generally speaking, the blending of materials will affect the water absorption of the resulting product, such as Huangsheng [2] found that the hydrogel prepared by PVP / PAA blend has strong water absorption; in addition, the cross-linking of the material will also affect the water absorption of the product, such as Zhou Jianan [3] Crosslinking time has been found to affect the water absorption of chitosan / gelatin composite microspheres. The improvement in cycle number achieved by this method may be due to the fact that polyvinyl alcohol is somewhat heat-sensitive and also absorbs water. By mixing it with polyethylene oxide and sodium polyacrylate, the imbalance between water absorption and water extrusion can be mitigated. The specific mechanism behind this is yet to be determined.

[0034] It is worth noting that the present invention uses a PVC thin layer as the base material, but those skilled in the art will appreciate that materials with mechanical properties (especially bending properties) comparable to those of the PVC thin layer can also be used as the base material of the present invention.

[0035] As an implementable specific solution of the present invention, N,N'-methylenebisacrylamide is the cross-linking agent, and the molar concentration of N,N'-methylenebisacrylamide is 0.0216% of acrylamide.

[0036] As an practicable embodiment of the present invention, the Ti3C2Tx MXene is prepared as follows: 3 g of Ti3C2Tx is added to 67 mL of 6M hydrochloric acid containing 6 g of LiF, followed by stirring at 60°C for 48 h, washing with deionized water, and centrifuging several times until the pH value of the centrifugal supernatant reaches above 6; then, the centrifuged sediment is dispersed in deionized water and ultrasonicated under an Ar2 atmosphere for 2 hours to obtain a layered exfoliated Ti3C2Tx MXene.

[0037] As a preferred embodiment of the present invention, the weight ratio of the Ti3C2Tx MXene and TiO2 mixture to solution A is 1:6; the weight ratio of Ti3C2Tx MXene and TiO2 is 2:1.

[0038] As a preferred embodiment of the present invention, the concentration of the dopamine aqueous solution is 30 mg / mL.

[0039] As a preferred embodiment of the present invention, the Fe 3+ The concentration of the ion solution is 0.05 mmol, and the Cu 2+ The concentration of the ion solution was 0.05 mmol.

[0040] As an implementable specific solution of the present invention, in step 3), the obtained fiber membrane is treated at 55° C. for 2 hours.

[0041] As an practicable specific solution of the present invention, in step (2), when the fixing is performed, the obtained skin material is placed in water, then applied to the blade base material, and then dried at 50-60°C, and then cooled at room temperature.

[0042] Another object of the present invention is to provide a stable, environmentally responsive, self-propelled flexible blade produced by the above-described method. Still another object is to provide the use of the stable, environmentally responsive, self-propelled flexible blade in the manufacture of blades for underwater sports equipment, such as blades for artificial robotic fish.

[0043] Beneficial effects of the present invention:

[0044] 1. The raw materials used in the present invention are all conventional materials in the field and are readily available. The preparation method of the flexible blades of the present invention is simple and does not require special processing conditions. Only the raw material ratio, relevant temperature and time need to be adjusted. The electrospinning process used is also a mature technology in the field.

[0045] 2. The flexible blade obtained by the present invention can use a relatively rigid material as the base material of the blade, and can achieve rapid, large-scale reversible self-driven deformation within a narrow temperature range; specifically, within the range of 28-30°C, it can achieve full curvature of 0.19 cm in 0.5s and 0.6s respectively. -1 thermally induced deformation and recovery deformation.

[0046] 3. The flexible blade obtained by the present invention has the ability to move stably. After completing 310 cycles of "deformation-recovery", it can still bend with a curvature of 0.10 cm in 1.2s and 1.6s in the range of 28-30°C. -1 thermally induced deformation and recovery deformation.

[0047] References cited in this section:

[0048] [1]Xu Huayu. Flexible self-actuated tactile sensor based on MXene blend[D]. Guangxi University, 2022.DOI:10.27034 / d.cnki.ggxiu.2022.002201.

[0049] [2] Huang Sheng, Li Cuizhen. Preparation and performance study of PVP / PAA blended hydrogel[J]. Jiangxi Chemical Industry, 2017, No.132(04):74-79.DOI:10.14127 / j.cnki.jiangxihuagong.2017.04.025.

[0050] [3]Zhou Jianan. Preparation and drug loading performance of chitosan / gelatin composite microspheres[D]. Hunan University of Science and Technology, 2012. DETAILED DESCRIPTION

[0051] The present invention is described in detail below through examples. It is necessary to point out that the following examples are only used to further illustrate the present invention and are not to be construed as limiting the scope of protection of the present invention. Non-essential improvements and adjustments made by those skilled in the art based on the above-mentioned invention still fall within the scope of protection of the present invention.

[0052] Explanation of some terms involved:

[0053] MBAA: N,N'-methylenebisacrylamide

[0054] TEMED: N,N,N',N'-tetramethylethylenediamine

[0055] AAm: Acrylamide

[0056] AAc: acrylic acid

[0057] Some of the raw materials involved:

[0058] PVA, polyethylene oxide: Wuxi Yatai United Chemical Co., Ltd.

[0059] Sodium polyacrylate: Wuxi Yatai United Chemical Co., Ltd.

[0060] Acrylamide, acrylic acid: Shanghai Aladdin Biochemical Technology Co., Ltd.

[0061] Example 1

[0062] Preparation of base material:

[0063] The commercially available PVC board was evenly cut into thin layers with a thickness of 0.5 mm, polished smooth with fine sandpaper, and cut into strips with a length of 5 cm and a width of 1 cm.

[0064] Skin material preparation:

[0065] 1.0662g of AAm, 0.21618g of AAc, potassium persulfate (1% by weight of the combined AAm and AAc), MBAA (0.0216% molar concentration of AAm), sodium polyacrylate (15% by weight of AAm), polyethylene oxide (15% by weight of acrylamide), polyvinyl alcohol (20% by weight of acrylamide), TEMED (20 μL), and deionized water (5 mL) were stirred vigorously to mix the components to obtain a homogeneous solution. A mixture of Ti3C2Tx MXene and TiO2 (particle size distribution between 100 and 200 nm) (Ti3C2Tx MXene and TiO2, with a weight ratio of 2:1) was added to the solution. Copper sulfide nanoparticles (particle size distribution between 80 and 200 nm) were then added, representing 15% by weight of AAm. The mixture was stirred slowly at room temperature for 12 hours to obtain the electrospinning solution. During electrospinning, the propulsion rate was 1.2 mL / h, the temperature was 32 °C, the receiving distance was 25 cm, and the obtained fiber membrane was placed at 55 °C for 2 hours. After obtaining the electrospun fiber membrane, the electrospun fiber membrane was placed in a dopamine aqueous solution (dopamine concentration was 30 mg / mL), cross-linked with EDC and NHS, and then immersed in Fe 3+ ion solution and (0.05mmol) Cu 2+ ion solution (0.05 mmol) for 24 hours, and then the residual ions were washed away with deionized water to obtain the skin material.

[0066] Flexible leaf preparation:

[0067] The obtained skin fiber was placed in deionized water for 2 minutes, applied to a thin layer of PVC (0.5 mm) of base material, dried at 55°C for 5 hours, and then cooled at room temperature (25-30°C) to obtain a flexible blade containing a thin layer of PVC.

[0068] Among them, the preparation method of Ti3C2Tx MXene is as follows: 3g Ti3C2Tx is added to 67 mL of 6M hydrochloric acid containing 6g LiF, then stirred at 60°C for 48 hours, washed with deionized water and centrifuged several times until the pH value of the centrifugal supernatant reaches above 6; then, the sediment after centrifugation is dispersed in deionized water and then ultrasonicated under Ar2 atmosphere for 2 hours to obtain layered exfoliated Ti3C2Tx MXene, which is crushed into powder (particle size 200~250μm).

[0069] Example 2

[0070] In addition to Fe 3+ The concentration of the ion solution is 0.02mmol, Cu 2+ Except that the concentration of the ion solution was 0.1 mmol, the rest was the same as in Example 1.

[0071] Example 3

[0072] In addition to Fe 3+ The concentration of the ion solution is 0.1mmol, Cu 2+ Except that the concentration of the ion solution was 0.02 mmol, the rest was the same as in Example 1.

[0073] Example 4

[0074] The reaction was the same as in Example 1, except that the weight of the copper sulfide nanoparticles was 10% of the AAm and the concentration of the dopamine aqueous solution was 50 mg / mL.

[0075] Example 5

[0076] The process was the same as in Example 1, except that the weight of the copper sulfide nanoparticles was 20% of the AAm and the concentration of the dopamine aqueous solution was 10 mg / mL.

[0077] Example 6

[0078] Except that the weight ratio of Ti3C2Tx MXene and TiO2 to the solution obtained in the previous step is 1:4, the rest is consistent with Example 1.

[0079] Example 7

[0080] Except that the weight ratio of Ti3C2Tx MXene and TiO2 to the solution obtained in the previous step is 1:7, the rest is consistent with Example 1.

[0081] Example 8

[0082] Except that the weight ratio of Ti3C2Tx MXene and TiO2 is 1:1, the rest is consistent with Example 1.

[0083] Comparative Example 1

[0084] The process was the same as in Example 1 except that TiO2 was not added, the weight ratio of Ti3C2Tx MXene to the solution obtained in the previous step was 1:5, polyethylene oxide and polyvinyl alcohol were not added, and the weight of sodium polyacrylate was 50% of that of AAm.

[0085] Comparative Example 2

[0086] Except for not adding polyethylene oxide, the rest is the same as Example 1.

[0087] Experimental Example 1

[0088] The products obtained in Examples 1-8 and Comparative Examples 1-2 were subjected to self-bending experiments and responsiveness experiments.

[0089] Self-bending and responsiveness experiments

[0090] The skin materials obtained in Examples 1-8 were subjected to phase transition temperature investigations. It was found that at a phase transition temperature of approximately 29°C, the water absorption of the flexible material rapidly increased from 100-120% at 28°C to 1100-1200% at 30°C.

[0091] The flexible leaves obtained in each example and each comparative example were placed in a 28°C water bath, and then transferred to a 30°C water bath. A high-speed camera was used to observe the deformation and the corresponding time. The results are shown in Table 1.

[0092] Table 1

[0093]

[0094] As shown in Table 1, while Comparative Example 1 (i.e., Example 1 in "A Sensitive Photothermal Self-Driven Flexible Blade and Its Preparation Method") achieved the best bending curvature and response time during the first cycle, the flexible blade obtained by the present invention also achieved similarly good results during the first cycle.

[0095] The flexible blades obtained in Examples 1-8 and Comparative Examples 1-2 were subjected to deformation-recovery experiments. The flexible blades were first placed in a 28°C water bath, then transferred to a 30°C water bath, and then transferred from the 30°C water bath to a 28°C water bath. The bending curvature and response time were observed using a high-speed camera. The results showed that, after increasing the number of cycles to 20, the flexible blade obtained in Comparative Example 1 could only complete a bending curvature of 0.11 cm in 1.7s and 2.3s in the 28-30°C range. -1 Thermal deformation and recovery deformation; after 100 cycles, 0.1cm -1The thermal deformation has reached 21s; compared with the flexible blade obtained in Example 2, after the number of cycles was increased to 20, the bending curvature of 0.04cm could only be completed in 7.6s and 18.9s in the range of 28~30℃. -1 thermally induced deformation and recovery deformation.

[0096] The flexible leaves obtained in Examples 1-8 can also obtain 0.10cm -1 The results of thermal deformation and recovery cycles are shown in Table 2.

[0097] Table 2

[0098]

[0099] By recording, we can get 0.10cm -1 When the number of cycles of thermal deformation and recovery deformation is calculated, the response time of thermal deformation and recovery deformation of each embodiment is within 1.8s and 2.0s, respectively. Among them, the response time of thermal deformation and recovery deformation of Example 1 is 1.2s and 1.6s, respectively.

[0100] Since the technical solution of this patent is based on the inventor's separately applied patent "A Sensitive Photothermal Self-Driven Flexible Blade and Its Preparation Method", the inventor has also recorded the preliminary experiments of the aforementioned patent in this patent to make it easier for people in this field to understand this patent technology.

[0101] Preliminary experiment:

[0102] When introducing the embodiments of the present invention, preliminary experiments conducted by the inventors before obtaining the technical solution of the present invention are first introduced so that people in this field can better understand the present invention.

[0103] 1. Preparation of skin fiber

[0104] Scheme 1: Refer to Xin-Jie Luo et al. [1] Ti3C2Tx MXene material was prepared by adding 3g of Ti3C2Tx to 67mL of 6M hydrochloric acid containing 6g of LiF, then stirring at 60°C for 48h, washing with deionized water and centrifuging several times until the pH value of the centrifugal supernatant reached above 6; then, the sediment after centrifugation was dispersed in deionized water and ultrasonicated under Ar2 atmosphere for 2h to obtain layered exfoliated Ti3C2Tx MXene, which was crushed into powder (particle size 200-250μm).

[0105] Ti3C2Tx MXene powder was mixed with a PVA aqueous solution (PVA concentration of 20 w / w%) at a weight ratio of 1:5 and electrospun to produce sheath fiber 1 (fiber thickness 1.2 mm). The electrospinning process was performed at a propulsion rate of 1.6 mL / h, a temperature of 37°C, and a receiving distance of 25 cm.

[0106] Scheme 2: Ti3C2Tx MXene, acrylic acid, acrylamide, sodium hydroxide, potassium persulfate, and PVA from Scheme 1 were prepared in a weight ratio of 1:5.6:5.5:1.55:0.06:6. PVA was dissolved in water to prepare a PVA aqueous solution. Acrylic acid was stirred in deionized water, sodium hydroxide was added and stirring continued, and finally acrylamide was added and stirred again to obtain Solution A. Solution A was added dropwise to the PVA aqueous solution under high-speed stirring. Nitrogen was then purged to remove air. Potassium persulfate was then added and stirred at 50°C for 2 hours and then at 59°C for 5 hours to prepare an aqueous solution with a solute weight fraction of 18%. Ti3C2Tx MXene was then added to the resulting aqueous solution in a weight ratio of 1:5. The mixture was stirred evenly, and glutaraldehyde was added (to a final concentration of 3%) to obtain a spinning solution. Electrospinning was performed to produce sheath fiber 2 (fiber thickness 1.2 mm). The electrospinning process was performed at a feed rate of 1.1 mL / h, a temperature of 37°C, and a receiving distance of 25 cm.

[0107] Scheme 3: Acetone and DMF were mixed in a 1:4 weight ratio. Polyvinylidene fluoride (PVDF) was added at a concentration of 75% acetone by weight and mixed thoroughly to obtain an electrospun fiber solution. Ti3C2Tx MXene (obtained using the same method as in Scheme 1) was added to the electrospun fiber solution at a concentration of 150% acetone by weight. The solution was stirred slowly at room temperature for 12 hours. Electrospinning was then performed to obtain skin fiber 3 (fiber thickness 1.2 mm). The electrospinning process was performed at a feed rate of 1.5 mL / h, a temperature of 37°C, and a receiving distance of 25 cm.

[0108] Scheme 4: Combine 1.0662g acrylamide, 0.21618g acrylic acid, potassium persulfate (1% by weight of the combined AAm and AAc), MBAA (0.0216% molar concentration of the combined AAm and AAc), TEMED (20μL), and deionized water (5mL) with vigorous stirring to mix the components and obtain a homogeneous solution. Ti3C2Tx MXene (obtained using the same method as in Scheme 1) was added to the solution at a weight ratio of 1:5 and stirred slowly at room temperature for 12 hours to obtain an electrospinning solution. Electrospinning was performed at a feed rate of 1.2mL / h, a temperature of 32°C, and a receiving distance of 25cm. The resulting fiber membrane was incubated at 55°C for 2 hours to obtain sheath fiber 4 (fiber thickness 1.2mm).

[0109] Scheme 5: Based on Scheme 4, without adding Ti3C2Tx MXene, the rest are the same.

[0110] Scheme 6: Based on Scheme 4, sodium polyacrylate with a weight ratio of 50% of AAm was added when preparing the electrospinning solution, and the rest was consistent with Example 4.

[0111] Scheme 7: Based on Scheme 6, after obtaining the electrospun fiber membrane, place the membrane in a dopamine aqueous solution (dopamine concentration: 30 mg / mL) and add EDC and NHS for cross-linking. The final concentrations of EDC and NHS are 0.0192 g / mL and 0.0115 g / mL, respectively.

[0112] 2. Investigation of Self-Bending

[0113] The skin fibers obtained in Schemes 1 to 4 were placed in deionized water for 2 minutes, applied to a stainless steel sheet, dried at 55°C for 5 hours, and then cooled at room temperature (25-30°C). The fiber membrane was then peeled off from the stainless steel sheet to obtain a flexible material.

[0114] In a water tank, a flexible material was clamped with a clamp and submerged in deionized water at 28°C. The flexible material was perpendicular to the bottom of the tank and irradiated with an 808nm (100mW) laser horizontally at a distance of 15cm. The bending behavior of the flexible material obtained from each solution was observed. Within 5 minutes of irradiation, a high-resolution camera was used to photograph the bending angle, as shown in Table 3:

[0115] Table 3

[0116]

[0117] Note: The values in the above table are rounded to two decimal places. The same applies to other tables expressing curvature.

[0118] As shown in Table 3, when Ti3C2Tx MXene powder is electrospun into PVA fibers, the resulting fibers basically lose their self-bending properties. [1] et al. directly formed Ti3C2Tx MXene into thin layers, but the resulting self-bending properties were significantly different. This may be due to the inherent thermal sensitivity of LDPE, which Ti3C2Tx MXene can promote in response to heat and self-curling. However, in PVA fibers, due to the low thermal responsiveness of PVA and the inability of Ti3C2Tx MXene to promote thermal response, the resulting fibers exhibited little deformation. Similarly, Scheme 2 also failed to produce significant self-bending deformation.

[0119] In Scheme 3, the inventors replaced PVA and other materials in the electrospinning solution with polyvinylidene fluoride, but still did not find that the resulting product had the corresponding thermal response self-bending deformation. It is worth noting that this material has been reported to have self-powered capability in other reports. [2] .

[0120] In scheme 4, the inventors found that the obtained flexible material has a certain self-bending effect. Through experiments, it was found that the self-bending curvature reached 0.04 cm after 125 seconds. -1 , and maintained until the end of the experiment. This may be because the materials used in Scheme 4 are heat-sensitive, and the resulting fiber membrane has stronger water absorption when the temperature rises, resulting in corresponding deformation. For Scheme 5, it can be seen that the addition of Ti3C2Tx MXene has a significant impact on the self-bending deformation. The reason may be that Ti3C2Tx MXene is also heat-absorbing, which promotes the self-bending properties of the resulting flexible material. For Scheme 6, it can be seen that blending sodium polyacrylate with the materials in Scheme 4 will slightly affect the self-bending effect of the resulting flexible material.

[0121] Surprisingly, in Scheme 7, after the inventors modified the fiber membrane obtained in Scheme 6 with dopamine, the resulting flexible material produced a curvature change of 0.23 after 8 seconds and maintained it until the end of the experiment.

[0122] 3. Responsiveness inspection

[0123] Inspired by Scheme 7, the inventors investigated the temperature and time response of the flexible material obtained in Scheme 7. They found that the phase transition temperature of the material obtained in Scheme 7 is around 29°C, and the water absorption of the flexible material rapidly increases from 100% at 28°C to 1100% at 30°C. This indicates that the flexible material obtained in Scheme 7 has high temperature-sensitive deformation properties.

[0124] 5. Optimize the experiment

[0125] Through the investigation of the above schemes, the invention obtains a flexible material with high sensitivity and thermal response deformation.

[0126] However, since blades usually require higher strength, the rigidity of the base material is usually larger, which makes it difficult for ordinary flexible materials to be used as blade skin materials. In this part of the experiment, the inventors used PVC (polyvinyl chloride) as the base material of the blade to examine the self-driven curling ability of the blade when the flexible material obtained in the aforementioned scheme 7 was used as the skin material. The specific preparation method is: the skin fiber obtained in scheme 7 is placed in deionized water for 2 minutes, applied on a thin layer of PVC (0.5mm), and then dried at 55°C for 5 hours, and then placed at room temperature (25-30°C) to cool, to obtain a flexible blade containing a thin layer of PVC. The same self-bending investigation method as mentioned above was used for the investigation, and it was found that the bending curvature of the obtained flexible blade was only 0.06cm within 5 minutes of irradiation. -1 .

[0127] On this basis, the inventors explored the following technical solutions to further improve the self-driven bending performance:

[0128] Scheme 8: Based on Scheme 7, the cross-linked electrospun fiber membrane is immersed in Fe 3+ ion solution (0.05 mmol) for 24 hours, and then the residual ions were washed away with deionized water to obtain the skin material 8.

[0129] Scheme 9: Based on Scheme 8, the electrospun fiber membrane was also treated with 0.05 mmol of Cu 2+ The ion solution was soaked for 24 hours, and the rest remained the same as in Scheme 8 to obtain the skin material 9.

[0130] Scheme 10: Based on Scheme 8, Fe 3+ The ion solution was replaced with Mg of the same concentration. 2+ ion solution, and the rest remains the same as Scheme 8 to obtain the skin material 10.

[0131] Scheme 11: Based on Scheme 10, the electrospun fiber membrane is also coated with Cu 2+ The ion solution was soaked for 24 hours, and the rest remained the same as in Scheme 8 to obtain the skin material 11.

[0132] Scheme 12: Based on Scheme 9, when preparing the electrospinning solution, copper sulfide nanoparticles (particle size distribution is 80~200nm) with a weight of 15% of AAm are added, and the rest remain the same as Scheme 9 to obtain skin material 12.

[0133] As shown in Table 4, when Fe 3+ ions, the self-driven bending performance of the flexible blade was enhanced, but the magnitude was small. Inspired by this, the inventors tried other ions Mg 2+, but no effect was found on the self-driven bending performance of the flexible blade; but it was found that the addition of Fe 3+ ions and Cu 2+ After ionization, the self-driven bending performance of the flexible blade was significantly enhanced. Surprisingly, the flexible blade prepared by the skin material obtained in Scheme 12 had a bending curvature of 0.17 cm at an irradiation time of 12 seconds. -1 , reaching 0.21cm at 18s -1 , and keep it until the end of the experiment.

[0134] Table 4

[0135]

[0136] At this point, the inventors have completed the development and exploration of self-driven flexible blades with high sensitivity and photothermal response.

[0137] A responsiveness experiment was conducted on the flexible blade produced in Scheme 12. The flexible blade was first placed in a 28°C water bath and then transferred to a 30°C water bath. A high-speed camera was used to photograph and observe its deformation. The results showed that after being transferred to the 30°C water bath, the flexible blade bent within 0.5 seconds with a curvature of 0.19 cm. -1 When it was transferred to a 28°C water bath, it recovered within 0.6 seconds (curvature -0.19 cm -1 ).

[0138] References cited in this section:

[0139] [1]Luo XJ, Li L, Zhang HB, et al. Multifunctional Ti3C2Tx MXene / Low-Density Polyethylene Soft Robots with Programmable Configuration for Amphibious Motions[J]. ACS applied materials&interfaces, 2021(38):13.

[0140] [2]Xu Huayu. Flexible self-actuated tactile sensor based on MXene blend[D]. Guangxi University, 2022.

Claims

1. A method for preparing an environmentally responsive self-propelled flexible blade with stable motion, characterized in that: The preparation method comprises the following steps: (1) Preparation of blade skin materials: 1) Acrylamide and acrylic acid are prepared in a molar ratio of 5:1, potassium persulfate is added to a crosslinker, N,N,N',N'-tetramethylethylenediamine, sodium polyacrylate, polyethylene oxide, and polyvinyl alcohol in a solution containing 1% of the total weight of acrylamide and acrylic acid, and the mixture is uniformly mixed in water to obtain solution A; 2) Add a mixture of Ti3C2Tx MXene and TiO2 to solution A at a weight ratio of 1:4-7, then add copper sulfide nanoparticles and stir evenly to obtain solution B; 3) Electrospinning solution B was used as the electrospinning solution to obtain a fiber membrane, and the obtained fiber membrane was treated at 50-60°C for 1-3 hours; then, the fiber membrane was placed in a dopamine aqueous solution and cross-linked with EDC and NHS; After crosslinking, it was immersed in Fe 3+ Ionic solution and Cu 2+ After 12 to 36 hours in the ion solution and washing the residual ions with water, the blade skin material is obtained; (2) placing the skin material obtained in step (1) on the blade base material, and fixing it to obtain the environmentally responsive self-driven flexible blade with stable motion; Among them, the volume ratio of N,N,N',N'-tetramethylethylenediamine to water is 1:250; the weight of sodium polyacrylate is 15% of acrylamide; the weight of polyethylene oxide is 15% of acrylamide, and the weight of polyvinyl alcohol is 20% of acrylamide; the weight ratio of Ti3C2TxMXene to TiO2 is 1~2:1; the weight of copper sulfide nanoparticles is 10~20% of the weight of acrylamide; the concentration of dopamine aqueous solution is 10~50mg / mL; Fe 3+ The concentration of the ion solution is 0.02mmol-0.1mmol; Cu 2+ The concentration of the ion solution is 0.02mmol-0.1mmol; The blade base material includes a thin layer of PVC, and the thickness ratio of the base material to the skin material is not higher than 5:

12.

2. The preparation method according to claim 1, characterized in that N,N'-methylenebisacrylamide is the cross-linking agent, and the molar concentration of N,N'-methylenebisacrylamide is 0.0216% of acrylamide.

3. The preparation method according to claim 1, characterized in that The Ti3C2Tx MXene was prepared by adding 3 g of Ti3C2Tx to 67 mL of 6M hydrochloric acid containing 6 g of LiF, stirring at 60°C for 48 h, washing with deionized water, and centrifuging several times until the pH value of the centrifugal supernatant reached above 6. The centrifuged sediment was then dispersed in deionized water and sonicated under an Ar atmosphere for 2 h to obtain exfoliated Ti3C2Tx MXene.

4. The preparation method according to claim 1 or 3, characterized in that The weight ratio of the Ti3C2Tx MXene and TiO2 mixture to solution A is 1:6; the weight ratio of Ti3C2Tx MXene and TiO2 is 2:

1.

5. The preparation method according to claim 1, characterized in that The concentration of the dopamine aqueous solution is 30 mg / mL.

6. The preparation method according to claim 1, characterized in that Fe 3+ The concentration of the ion solution is 0.05 mmol, and the Cu 2+ The concentration of the ion solution was 0.05 mmol.

7. The preparation method according to claim 1, characterized in that In step 3), the obtained fiber membrane is treated at 55° C. for 2 hours.

8. The preparation method according to claim 1, characterized in that In step (2), when the fixing is performed, the obtained skin material is placed in water, then applied to the blade base material, and then dried at 50-60°C, and then cooled at room temperature.

9. An environmentally responsive self-actuated flexible blade with stable motion, characterized in that: The environmentally responsive self-driven flexible blade with stable motion is prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the environmentally responsive self-driven flexible blade with stable motion as claimed in claim 9 in preparing blades for underwater sports equipment.

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